The present invention relates to apparatus for analyzing line sequential binary data representative of features present in a two-dimensional image.
Where it is desired to process binary data in a two-dimensional format derived from an optical image or the like, it is preferable to represent the features present therein by the smallest possible amount of data. This reduces the required memory capacity where the data is subsequently processed by computer and also reduces processing time, since the amount of data to be processed is minimal. It is also advantageous to convert the data from bit format to word format for computer processing.
One system for producing a binary image for analyzing the metallic patterns on a circuit board is disclosed in U.S. Pat. No. 4,152,723, in the names of Donald H. McMahon and Colin G. Whitney. McMahon et al disclose an apparatus capable of generating binary data in line sequential format to indicate the presence or absence of metallic conductors at selected binary image points on the surface of a circuit board. In this apparatus, a beam of light scans over the surface of the circuit board in sequential parallel scans thus to illuminate the metallic conductors and the insulating substrate on which they are disposed. When the beam is incident on an exposed portion of the insulating substrate, a fluorescent emission therefrom is detected and a binary signal having a first state is generated by the apparatus. When the beam is incident on a metallic conductor, no fluorescent emission results such that in the absence of a detected fluorescent emission, the apparatus produces a binary signal of a second state complementary to the first state. Through the provision of means for synchronizing the scan of the beam with the binary signal produced by the apparatus, a binary image of the surface of the circuit board is generated.
Such an apparatus is capable of producing a vast amount of data. For example, where such apparatus is used to generate a binary image of the surface of a forty inch square circuit board, and where the scanning beam has a one mil resolution such that the binary image points are separated by one mil, a total of 1.6 billion bits of data will be generated by the scanning apparatus. It is desirable to provide an apparatus for reducing this vast amount of data and for processing it simultaneously with the scan of the circuit board so that the need for storing this data for non-real time processing may be avoided.
In addition, an apparatus for processing such data should be capable of distinguishing data which indicates real features on the surface of the board from false data resulting from source of error such as optical noise, non-uniform motion of the scanner caused by bearing noise, and problems associated with image quantization. Bearing noise in the scanner system will result in a shift in scanner position either in a direction of the fast or slow scan resulting in an offset in the image and the appearance of a jog or corner on the surface of the board where in fact there is no such feature. Image quantization is the operation of assigning a discrete binary value to the data representing features at selected binary data points on the surface of the board. Due to limits of resolution, the scanning beam at a given point in time may fall upon an edge feature such that a portion of the beam is incident on the substrate and a portion is incident on metal. Since the fluorescent emission detected by the scanning apparatus is at a very low level, the presence of optical or electrical noise may cause the scanning apparatus to generate either one binary signal level or its complement without regard to the actual feature scanned.
A further complication is introduced where the scanning apparatus is used to scan a circuit board having a metal backing. In such case, the threshold between the level of detected fluorescence which will determine the generation of one binary signal level or its complement must be set very close to the black level such that the sensitivity of the scanning apparatus to optical noise is significantly increased.
In the art of automated character recognition, it is desired to provide a means for rapid and accurate machine reading of information bearing characters, such as alphanumerics. Ideally, an apparatus should be provided which is capable of reliably recognizing handwritten and machine-produced characters despite variations in character size and style, and retaining essential information for reproduction of such characters. At the same time, such an apparatus should be capable of operation in real time; that is, without the need for excessive storage of character information.